Reduced growth hormone secretion in obesity is associated with smaller LDL and HDL particle size

Effect of One-Year Growth Hormone Therapy on Cardiometabolic Risk Factors in Boys with Obesity

It has been recognized that people with obesity are more likely to have low growth hormone secretion. Recent studies have also confirmed that the abnormalities of the growth hormone/insulin-like growth factor 1 axis were associated with cardiovascular complications in people with obesity. However, little is known about whether recombinant human growth hormone therapy could improve cardiovascular and metabolic risks in obese children. This study aims to evaluate the effect of one-year growth hormone therapy on obesity-related comorbidities and to assess the safety in Chinese boys with obesity. Eighteen boys with obesity were treated with recombinant human growth hormone for one year. Anthropometric measurements, endocrine testing, and cardiovascular risk markers were performed in all obese boys in baseline, and follow-up visits were performed at 3 months, 6 months, 9 months, and one year, respectively. After one year of recombinant human growth hormone treatment, the body mass index standard deviation scores decreased (P < 0.001) and insulin-like growth factor 1 levels increased (P < 0.001). GH treatment also reduced low density lipoprotein cholesterol (P < 0.001), total cholesterol (P < 0.001), triglycerides (P=0.042), and alanine aminotransferase (P=0.027) when compared with the baseline. One-year of recombinant human growth hormone treatment could improve cardiometabolic risk markers, without adverse effects on glucose homeostasis in boys with obesity.

Somatotropic Axis and Obesity: Is There Any Role for the Mediterranean Diet?

Obesity is associated with reduced spontaneous and stimulated growth hormone (GH) secretion and basal insulin-like growth factor I (IGF-1) levels—which in turn is associated with increased prevalence of cardiovascular risk factors. The aim of this study was to investigate: (1) the association of somatotropic axis with cardiometabolic status; (2) the association of somatotropic axis with the Mediterranean diet and nutritional pattern in people with obesity. Cross-sectional observational study was carried out in 200 adult women, aged 36.98 ± 11.10 years with severe obesity (body mass index—BMI of 45.19 ± 6.30 kg/m²). The adherence to the Mediterranean diet and the total calorie intake was assessed. Anthropometric measurements, body composition and biochemical profile were determined along with Growth Hormone (GH)/Insulin like Growth Factor 1 (IGF-1) axis and insulin resistance (homeostatic model assessment for insulin resistance—HoMA-IR). The enrolled subjects were compared after being divided according to GH peak response and according to IGF-1 standard deviation scores (SDS). Derangements of GH peak were detected in 61.5% of studied patients while IGF-1 deficiency was detected in 71% of the population. Both blunted GH peak response and IGF-1 SDS were indicators of derangements of somatotropic axis and were associated with comparable results in terms of cardiometabolic sequelae. Both GH peak and IGF-1 levels were inversely associated with anthropometric and metabolic parameters. The adherence to the Mediterranean diet predicts GH peak response. Fatty liver index (FLI), fat mass (FM) and phase angle (PhA) were predictive factors of GH peak response as well. In conclusion derangements of somatotropic axis is associated with a worse cardiometabolic profile in people with obesity. A high adherence to the Mediterranean diet—and in particular protein intake—was associated with a better GH status.

Reduced peak stimulated growth hormone is associated with hyperuricemia in obese children and adolescents

The purpose of the study is to investigate whether reduced peak GH response to arginine-levodopa test is associated with hyperuricemia in obese children and adolescents. The study population consisted of a total sample of 78 obese and 30 normal-weight children and adolescents without known hypopituitarism. All participants underwent clinical examination and GH stimulation testing. IGF-1, lipid profile and other metabolic markers were assessed. The obese subjects were then divided into two groups according to the serum levels of uric acid. Results show that obese subjects had significantly lower peak GH, lower IGF-1 and similar height SDS than those in the control group. Children with hyperuricemia had significantly lower peak stimulated GH compared with non-hyperuricemia obese subjects. Results from logistic regression model showed that peak GH were negatively associated with hyperuricemia after controlling for age, gender, tanner stage, BMI SDS, IGF-1, blood pressure, HOMA-IR, lipids status. These data indicate that lower peak GH is positively associated with hyperuricemia in obese children and adolescents without known hypothalamic/pituitary disease after controlling BMI and insulin resistance, as well as other cardiometabolic risk factors.

Effects of recombinant human growth hormone administration on cardiovascular risk factors in obese children with relative growth hormone deficiency

Background

Based on the sample of obese children with relative growth hormone deficiency (GHD), the objective of our study was to determine the effects of rhGH treatment on cardiovascular risk factors, including body mass index (BMI), lipid levels and glucose metabolism index.

Methods

A total of 43 obese children with relative GHD were included in our final analysis. The obese subjects were divided into two groups: recombinant human growth hormone (rhGH) treatment group and untreated control group.

Results

After 6 months, subjects in the rhGH treatment group had significant reductions in BMI standard deviation scores (SDS) compared with controls (2.32 ± 0.85 vs. 2.80 ± 0.61; P = 0.041), and Insulin-like growth factor 1(IGF-1) level increased during rhGH treatment, in comparison with the control group (702.91 ± 246.03 vs. 348.30 ± 131.93 ng/mL, P < 0.001). GH treatment reduced low density lipoprotein cholesterol (LDL-C) (2.20 ± 0.45 vs. 2.63 ± 0.76 mmol/L, P = 0.027), aspartate aminotransferase (AST) (21.26 ± 5.72 vs. 32.30 ± 17.68 mmol/L, P = 0.006) as well as alanine aminotransferase (ALT) (16.70 ± 6.72 vs. 45.20 ± 46.62 mmol/L, P = 0.002), and increased high density lipoprotein cholesterol (HDL-C) (1.45 ± 0.40 vs. 1.19 ± 0.23 mmol/L, P = 0.016) levels compared with the control group.

Conclusion

RhGH treatment for 6 months on obese children with relative GHD reduces BMI SDS, stabilize IGF-1 levels, and exerts beneficial effects on blood lipid profiles and live enzyme compared with untreated control group. Moreover, GH administration has no significant effects on increased insulin resistance and no adversely effect on glucose homeostasis.

Slim Body Weight Is Highly Associated With Enhanced Lipoprotein Functionality, Higher HDL-C, and Large HDL Particle Size in Young Women

There has been no information about the correlations between body weight distribution and lipoprotein metabolism in terms of high-density lipoproteins-cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP). In this study, we analyzed the quantity and quality of HDL correlations in young women (21.5 ± 1.2-years-old) with a slim (n = 21, 46.2 ± 3.8 kg) or plump (n = 30, 54.6 ± 4.4 kg) body weight. Body weight was inversely correlated with the percentage of HDL-C in total cholesterol (TC). The plump group showed 40% higher body fat (26 ± 3 %) and 86% more visceral fat mass (VFM, 1.3 ± 0.3 kg) than the slim group, which showed 18 ± 2% body fat and 0.7 ± 0.2 kg of VFM. Additionally, the plump group showed 20% higher TC, 58% higher triglyceride (TG), and 12% lower HDL-C levels in serum. The slim group showed 34% higher apoA-I but 15% lower CETP content in serum compared to the plump group. The slim group showed a 13% increase in particle size and 1.9-fold increase in particle number with enhanced cholesterol efflux activity. Although the plump group was within a normal body mass index (BMI) range, its lipid profile and lipoprotein properties were distinctly different from those of the slim group in terms of CETP mass and activity, HDL functionality, and HDL particle size.

Reconstituted High-Density Lipoprotein Containing Human Growth Hormone-1 Shows Potent Tissue Regeneration Activity with Enhancement of Anti-Oxidant and Anti-Atherosclerotic Activities

BACKGROUND

Human growth hormone-1 (GH-1), somatotropin, is a peptide hormone that stimulates cell division in tissues such as bone and cartilage.

METHODS

To compare physiological activities in lipid-free and lipid-bound states, we expressed and incorporated GH-1 in reconstituted high-density lipoprotein (rHDL).

RESULTS

GH-1 was expressed and purified using the pET30(a) vector and an Escherichia coli expression system. Purified GH-1 (at least 98% purity, 23 kD) was characterized and synthesized with apolipoproteinA-I (apoA-I), 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and cholesterol. Secondary structure analysis of GH-1 revealed 54% α-helical content in a lipid-free state and 65% α-helical content in a lipid-bound state along with blue-shifted tryptophan movement (around 2 nm). GH-1 caused less uptake of oxidized low-density lipoprotein (oxLDL) into macrophages and inhibited senescence of dermal cells in a dose-dependent manner. GH-1 in a lipid-bound state exerted stronger inhibitory activity than in a lipid-free state, indicating improved anti-atherosclerotic activity due to the lipid formulation. In a fin regeneration experiment using zebrafish (17 weeks old, n=9), GH-1 showed its highest regeneration speed without any side effects. GH-1-rHDL containing apoA-I showed 2.3-fold and 1.6-fold higher regeneration speeds than lipid-free GH-1 (in native state) and lipid-bound GH-1, respectively.

CONCLUSION

Incorporation of GH-1 and apoA-I in HDL enhanced tissue regeneration activity of amputated tail fin, indicating a synergetic effect between GH-1 and apoA-I in a lipid-bound state.

Effects of growth hormone-releasing hormone on visceral fat, metabolic, and cardiovascular indices in human studies

Increased visceral adipose tissue (VAT) is associated with reductions in endogenous GH secretion, possibly as a result of hyperinsulinemia, increased circulating free fatty acid, increased somatostatin tone, and reduced ghrelin. Reduced GH may, in turn, further exacerbate visceral fat accumulation because of decreased hormone-sensitive lipolysis in this depot. Data from multiple populations demonstrate that both reduced GH and increased VAT appear to contribute independently to dyslipidemia, increased systemic inflammation, and increased cardiovascular risk. The reductions in GH in states of visceral adiposity are characterized by reduced basal and pulsatile GH secretion with intact pulse frequency. Treatment with GH-releasing hormone (GHRH) provides a means to reverse these abnormalities, increasing endogenous basal and pulsatile GH secretion without altering pulse frequency. This review describes data from HIV-infected individuals and individuals with general obesity showing that treatment with GHRH significantly reduces visceral fat, ameliorates dyslipidemia, and reduces markers of cardiovascular risk. Further research is needed regarding the long-term efficacy and safety of this treatment modality.

The complex relationship between obesity and the somatropic axis: the long and winding road

Despite the considerable body of evidence pointing to a possible relationship between the state of the adipose tissue depots and regulation of the somatotropic axis, to date the relationship between obesity and low growth hormone (GH) status remains incompletely understood. The low GH status in obesity is mainly considered as a functional condition, largely reversible after a sustained weight loss. Moreover, due to the effects of the adiposity on the regulation of the somatotropic axis, the application of GH stimulation tests in obesity may also lead to an incorrect diagnosis of GH deficieny (GHD). On the other hand, similar to patients with GHD unrelated to obesity, the reduced GH response to stimulation testing in obese individuals is associated with increased prevalence of cardiovascular risk factors and detrimental alterations of body composition, which contribute to worsening their cardio-metabolic risk profile. In addition, the reduced GH secretion may result in reduced serum insulin-like growth factor (IGF)-1 levels, and the concordance of low peak GH and low IGF-1 identifies a subset of obese individuals with high cardiovascular risk. Furthermore, after weight loss, the normalization of the GH response and IGF-1 levels may or may not occur, and in patients undergoing bariatric surgery the persistence of a low GH status may affect the post-operative outcomes. In this review, we will provide an overview on some clinically relevant aspects of the relationship between obesity axis and the somatotropic axis in the light of the recently published research.

Lipid patterns in treated growth hormone deficient children vs. short stature controls

CONTEXT

Previous studies in adults with growth hormone (GH) deficiency have substantiated an increased risk of cardiovascular events. This risk has been attributed to an unpropitious lipid profile, increased abdominal mass, and higher incidence of metabolic syndrome. In these studies, a collateral observation has been a negative correlation between IGF-1 levels and lipid profiles. Longitudinal studies are lacking in children with GH-deficiency wherein the various lipid subfractions after GH treatment were compared to matched GH-sufficient short stature controls. Our study examined changes in small lipid particles following GH treatment.

OBJECTIVE

The primary objective was to determine the effect of GH treatment on serum lipids in GH-deficient patients vs. short controls.

DESIGN, SETTING, AND PARTICIPANTS

This was a prospective, unblinded, case-controlled, 6-month trial conducted at a tertiary pediatric referral center. Patients were referred for short stature. Incorporating accepted criteria, the treatment group (n=18) was found to be GH-deficient, whereas the control group (n=13) was GH-sufficient. The two groups had near-identical short stature along in addition to baseline measurements of weight and BMI.

INTERVENTIONS

The treatment arm received 6 months of recombinant GH at standard doses.

MAIN OUTCOME MEASURES

The primary endpoint was the comparison of the lipoprotein subclasses and lipids between the two groups after 6 months.

RESULTS

With the exception of the intermediate density lipoprotein (IDL), there were no significant differences at baseline in serum lipid profiles between the GH-deficient children and the controls. After 6 months of therapy, there were statistically significant differences in Apo-B, LDL, and smaller lipoparticles (LDL-3 and non-HDL) in GH-treated children compared to untreated GH-sufficient short children.

CONCLUSIONS

Our findings indicate that GH replacement may improve cardiovascular outcome by favorably altering lipid profiles.

CD, Folkman K, Groblewski T, Ruze P. The vitamin D status of prison inmates

Introduction

There is no comprehensive, systematic analysis of the vitamin D status of prisoners in the scientific literature.

Objective

To investigate the vitamin D status and its determinants in US prison inmates.

Hypothesis

Given the uniformity of dietary intake amongst inmates, vitamin D status will be determined by non-dietary factors such as skin pigmentation, security level-, and the duration of incarceration.

Subjects and Methods

A retrospective study of 526 inmates (males, n = 502, age 48.6±12.5 years; females, n = 24, age 44.1±12.2) in Massachusetts prisons. Vitamin D sufficiency, insufficiency, and deficiency were respectively defined as a 25(OH)D concentration 75 nmol/L; 50 to 75 nmol/L; and <50 nmol/L. The Massachusetts Department of Correction Statement of Nutritional Adequacy stated that each inmate received the recommended daily allowance of vitamin D daily. Security level of incarceration was designated as minimum, medium, and maximum. Racial groups were categorized as Black, white, Asian, and Others.

Results

Serum 25(OH)D levels peaked in summer and autumn, and decreased in winter and spring. Vitamin D deficiency occurred in 50.5% of blacks, 29.3% of whites, and 14.3% of Asian inmates (p = 0.007). Black inmates had significantly lower serum 25(OH)D level than white inmates at the maximum security level (p = 0.015), medium security level (p = 0.001), but not at the minimum security level (p = 0.40). After adjusting for covariates black inmates at a maximum security level had a four-fold higher risk for vitamin D deficiency than white inmates at the same security level (OR 3.9 [95% CI 1.3–11.7].

Conclusions

The vitamin D status of prison inmates is determined by skin pigmentation, seasons, and the security level of incarceration.

Discordance of IGF-1 and GH stimulation testing for altered GH secretion in obesity

OBJECTIVE

To investigate the concordance/discordance of IGF-1 and peak stimulated GH in identifying subjects with reduced GH secretion and to determine the physiological significance of any discordance in obese subjects.

DESIGN, PATIENTS AND METHODS

95 obese and 43 normal weight men and women underwent measurement of IGF-1 and GH stimulation testing with GH releasing hormone (GHRH)-arginine. Reduced IGF-1 and GH secretion were defined using pre-determined cut-points. Cardiovascular disease risk was determined by measuring carotid intima-media thickness (cIMT). In a second study, IGF-1 was measured in 52 obese men and women who underwent GH stimulation testing and overnight frequent blood sampling. The association of IGF-1 and peak stimulated GH with parameters of endogenous GH secretion was assessed.

RESULTS

60% of obese subjects had normal IGF-1 and peak stimulated GH while 8.4% of obese subjects had reduced IGF-1 and GH secretion. Discordance rate for IGF-1 and peak GH was 31.6%. Subjects with both low IGF-1 and low peak GH had the highest cIMT, while subjects with both normal IGF-1 and peak GH had the lowest cIMT. Subjects with reduction in either IGF-1 or peak GH, had intermediate cIMT (P=0.02). IGF-1 and peak stimulated GH were associated with maximum and mean overnight serum GH and GH AUC as well as maximum peak mass and median pulse mass. Peak stimulated GH, but not IGF-1, was also associated with nadir overnight serum GH concentration and basal GH secretion.

CONCLUSION

Peak stimulated GH and IGF-1 demonstrate significant discordance in identification of subjects with reduced GH secretion in obesity. Subjects with reduction of either IGF-1 or peak GH had higher cIMT compared to subjects with both normal IGF-1 and peak GH. Subjects with reductions in both IGF-1 and peak GH had the highest cIMT. Peak GH, compared to IGF-1, has broader associations with various parameters of endogenous GH secretion which support its utility in identifying those with reduced GH secretion.

The effects of tesamorelin on phosphocreatine recovery in obese subjects with reduced GH

CONTEXT

Few studies have assessed the relationship between GH and mitochondrial function.

OBJECTIVE

The objective of this study was to determine the effects of improving IGF-I using a GHRH analog, tesamorelin, on mitochondrial function assessed by phosphocreatine (PCr) recovery using (31)P magnetic resonance spectroscopy in obese adults with reduced GH.

DESIGN

A total of 39 obese men and women with reduced GH secretion as determined by GHRH-arginine stimulation tests underwent magnetic resonance spectroscopy as part of a 12-month, double-blind, randomized, placebo-controlled trial comparing tesamorelin vs placebo. PCr recovery after submaximal exercise was assessed at baseline and at 12 months.

RESULTS

At baseline, there were no differences in age, sex, race/ethnicity, and GH or PCr parameters between tesamorelin and placebo. After 12 months, tesamorelin treatment led to a significantly greater increase in IGF-I than did placebo treatment (change, 102.9±31.8 μg/L vs 22.8±8.9 μg/L, tesamorelin vs placebo; P=.02). We demonstrated a significant positive relationship between increases in IGF-I and improvements in PCr recovery represented as ViPCr (R=0.56; P=.01). The association between IGF-I and PCr recovery was even stronger among subjects treated with tesamorelin only (ViPCr: R=0.71; P=.03). This association remained significant after controlling for age, sex, race, ethnicity, and parameters of body composition and insulin sensitivity (all P<.05).

CONCLUSIONS

Increases in IGF-I from 12 months of treatment with tesamorelin were significantly associated with improvements in PCr recovery parameters in obese men and women with reduced GH secretion, suggestive of improvements in mitochondrial function.

HDL-cholesterol in coronary artery disease risk: function or structure?

High-density lipoproteins (HDL) are inversely related with coronary artery disease (CAD) and HDL-cholesterol is the only standardized and reproducible parameter available to estimate plasma concentration of these lipoproteins. However, pharmacological interventions intended to increase HDL-cholesterol have not been consistently associated to an effective CAD risk reduction. Among patients with a myocardial infarction, 43 and 44% of men and women, respectively, had normal plasma levels of HDL-cholesterol, whereas genetic studies have failed to show a causal association between HDL-cholesterol and CAD risk. Instead, HDL functionality seems to be the target to be evaluated, but the existing methods are still poorly reproducible and far to be adapted to the clinical laboratory. HDL subclasses rise as a potential alternative for the evaluation of CAD risk; HDL subclasses are a surrogate of intravascular metabolism of these lipoproteins and probably of their functionality. Low levels of large HDL and increased proportions of small particles are the most remarkable features associated to an increased risk of type 2 diabetes mellitus (T2DM) or CAD. However, inflammation and other environmental factors are related with abnormal HDL structure, and, as a consequence, more prospective studies are needed to better support the clinical usefulness of HDL subclasses. New insights from proteome and lipidome profiles of HDL will provide potential HDL-related biomarkers in the coming years.

Lipoprotein subfractions in metabolic syndrome and obesity: clinical significance and therapeutic approaches

Small, dense low density lipoprotein (sdLDL) represents an emerging cardiovascular risk factor, since these particles can be associated with cardiovascular disease (CVD) independently of established risk factors, including plasma lipids. Obese subjects frequently have atherogenic dyslipidaemia, including elevated sdLDL levels, in addition to elevated triglycerides (TG), very low density lipoprotein (VLDL) and apolipoprotein-B, as well as decreased high density lipoprotein cholesterol (HDL-C) levels. Obesity-related co-morbidities, such as metabolic syndrome (MetS) are also characterized by dyslipidaemia. Therefore, agents that favourably modulate LDL subclasses may be of clinical value in these subjects. Statins are the lipid-lowering drug of choice. Also, anti-obesity and lipid lowering drugs other than statins could be useful in these patients. However, the effects of anti-obesity drugs on CVD risk factors remain unclear. We review the clinical significance of sdLDL in being overweight and obesity, as well as the efficacy of anti-obesity drugs on LDL subfractions in these individuals; a short comment on HDL subclasses is also included. Our literature search was based on PubMed and Scopus listings. Further research is required to fully explore both the significance of sdLDL and the efficacy of anti-obesity drugs on LDL subfractions in being overweight, obesity and MetS. Improving the lipoprotein profile in these patients may represent an efficient approach for reducing cardiovascular risk.

Lipoprotein subfractions in metabolic syndrome and obesity: clinical significance and therapeutic approaches

Small, dense low density lipoprotein (sdLDL) represents an emerging cardiovascular risk factor, since these particles can be associated with cardiovascular disease (CVD) independently of established risk factors, including plasma lipids. Obese subjects frequently have atherogenic dyslipidaemia, including elevated sdLDL levels, in addition to elevated triglycerides (TG), very low density lipoprotein (VLDL) and apolipoprotein-B, as well as decreased high density lipoprotein cholesterol (HDL-C) levels. Obesity-related co-morbidities, such as metabolic syndrome (MetS) are also characterized by dyslipidaemia. Therefore, agents that favourably modulate LDL subclasses may be of clinical value in these subjects. Statins are the lipid-lowering drug of choice. Also, anti-obesity and lipid lowering drugs other than statins could be useful in these patients. However, the effects of anti-obesity drugs on CVD risk factors remain unclear. We review the clinical significance of sdLDL in being overweight and obesity, as well as the efficacy of anti-obesity drugs on LDL subfractions in these individuals; a short comment on HDL subclasses is also included. Our literature search was based on PubMed and Scopus listings. Further research is required to fully explore both the significance of sdLDL and the efficacy of anti-obesity drugs on LDL subfractions in being overweight, obesity and MetS. Improving the lipoprotein profile in these patients may represent an efficient approach for reducing cardiovascular risk.

The role of psychobiological and neuroendocrine mechanisms in appetite regulation and obesity

Obesity is a multifactorial disease. Among its causes are physical inactivity and overeating. In addition, other factors may play an important role in the development of overweight/obesity. For example, certain hormones including leptin, insulin and ghrelin, may influence appetite and consequently body weight. Obesity frequently co-exists with metabolic disorders including dyslipidemia, hypertension and insulin resistance, thus constituting the metabolic syndrome which is characterized by increased cardiovascular risk. Lack of comprehensive knowledge on obesity-related issues makes both prevention and treatment difficult. This review considers the psychobiological and neuroendocrine mechanisms of appetite and food intake. Whether these factors, in terms of obesity prevention and treatment, will prove to be relevant in clinical practice (including reducing the cardiovas-cular risk associated with obesity) remains to be established.